Rubidium Iodide crystals are bcc in structure. Study about RbI crystal in present of two body body interaction has been observed some shortcomings especially with respect to the Cauchy violation, high dielectric constants, high electronic polarizabilities and phonon dispersion relation because of lack of many body terms. So overcome to these difficulties a new model proposed, van der Waals three body force shell model (VTBFSM) come in existence .Which incorporates the effects of the van der Waals interaction with long-range Coulomb interactions, three-body interactions and short-range second neighbour interactions in the framework of rigid shell model (RSM).The theoretical predictions achieved for Phonon dispersion, Debye temperature variations, two phonon Raman and infra red–absorption spectra for RbI. The obtained theoretical results are very close agreement with experimental result.
